Oblique Illumination Detector for Imprint Alignment
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Solution Overview
Problem
Existing imprint apparatuses face challenges in accurately detecting the relative positions of alignment marks on a substrate and a mold due to interference from unnecessary light, which degrades detection accuracy.
Innovation Solution
A detector system is designed with an illumination optical system that tilts the light to form a specific light intensity distribution on the pupil plane, and a detection optical system that blocks unnecessary light, allowing only interference light to pass through, thereby enhancing detection accuracy by using a dark-field configuration and oblique illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional illumination and detection optical systems are used to detect alignment marks, then the detection process can be performed, but unnecessary light (diffracted light or scattered light) mixes with the detection signal, degrading detection accuracy
Solution Approach 1:
The detection optical system is segmented into multiple functional components: an illumination optical system that provides oblique illumination, a beam splitter that separates illumination and detection paths, and a detection optical system with specific pupil plane configurations. This segmentation allows independent optimization of each component to eliminate unnecessary light while maintaining detection functionality.
Solution Approach 2:
The patent applies local quality by creating specific light intensity distributions at the pupil plane of the detection optical system. A bright field region and a dark field region are created in different areas of the pupil plane, allowing the system to selectively detect interference light from alignment marks while blocking unnecessary diffracted and scattered light in other regions.
2Measurement precision
If oblique illumination is used to improve detection accuracy, then detection precision can be enhanced, but the optical system complexity increases due to the need for specific light intensity distribution control
Solution Approach 1:
The beam splitter serves multiple functions: it directs illumination light from the illumination optical system onto the alignment marks, and simultaneously directs the reflected or transmitted light from the marks to the detection optical system. This multi-functionality reduces the need for separate optical paths and components, thereby managing system complexity while maintaining oblique illumination benefits.
Solution Approach 2:
The patent controls the light intensity distribution in the pupil plane dimension, creating specific bright and dark field regions. By manipulating the optical system to create this two-dimensional intensity distribution pattern, the system achieves superior light separation and detection accuracy without requiring complex mechanical adjustments or additional optical components.
3Measurement precision
If a pupil plane filter is used to block unnecessary light, then detection accuracy improves, but the device complexity increases due to additional optical components
Solution Approach 1:
The patent merges the illumination optical system and detection optical system into an integrated configuration using a beam splitter. The pupil plane filtering function is combined with the existing optical path design, where the beam splitter and optical elements work together to create the light intensity distribution that inherently blocks unnecessary light while detecting the desired interference patterns from alignment marks.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly improves the detection accuracy of relative positions by filtering out unnecessary light, allowing for precise alignment and pattern transfer in the imprint process.
Implementation Method 1
detection optical system configured to detect interference light of diffracted lights from the first mark and the second mark illuminated by the illumination optical system
Implementation Method 2
pupil plane of the detection optical system allows the interference light to pass through and block at least a part of light other than the interference light
Data Source
AI summary
A detector that detects relative positions of a first object and a second object in directions different from each other on a predetermined plane, includes an illumination optical system configured to illuminate a first mark provided on the first object and a second mark provided on the second object, and a detection optical system configured to detect interference light of diffracted lights from the first mark and the second mark illuminated by the illumination optical system. A light intensity distribution is formed, on a pupil plane of the illumination optical system, to illuminate the first mark and the second mark from a direction tilted with respect to a normal of the predetermined plane. A pupil plane of the detection optical system allows the interference light to pass through and block at least a part light other than the interference light.